There is conventionally used a refrigeration apparatus comprising a refrigerant circuit for carrying out a multistage compression refrigeration cycle, being a refrigeration apparatus provided with an intercooler and an oil separator. The intercooler cools a compressed refrigerant blown out from each stage of compression mechanism other than that of the highest stage. The oil separator separates a lubricating oil from the compressed refrigerant blown out from the compression mechanism in order to reduce the amount of oil rising at each stage during the cooling operation. The oil separator is usually installed on piping on a blow-out side of the compression mechanism, as is disclosed in Japanese Laid-open Patent Application No. 2009-257704.